Are you using twofish lockblocks? I've used them on the bars, but not the helmet. Is it a stable mount for the helmet?
3x175 lumens is pretty good! Right up there w/ my Trail Tech HID (500 lumens). Actually, that is assuming you run them in turbo mode. Do you? Do they get overly hot?
The mount in the photo is indeed a TwoFish Lockblock. For her helmet it works, but it does stick up too high in my opinion. But it is very stable and for the right helmet it will attached just fine (on some helmets, it won't). But there are other options that allow a lower-profile setup. Plus, the L2D is really rather long for a helmet light -- but it's what I use so I had it available to temporarily attach to her helmet to see how she would handle it.
I run the L2D only in turbo mode for the bike since the lower modes (to me) aren't bright enough for practical use on a bike at night. And with an adult rider pretty much riding without stopping (or stopping infrequently), turbo mode seems to be a non-issue in term so heat buildup. You have constant airflow cooling and I've never noticed much heat buildup at all when using it on the bike (compared to using it in turbo mode without the constant air flow to help keep it cool).
If I kid were using one, though, heat buildup could possible be an issue since they're more prone to stopping and maybe forgetting to turn the light off or down to a lower mode. But then again, it's being used at night with cooler temperatures, so maybe head buildup would be a non-issue all around, even if for a kid.
Expensive option for a young child, though. But the other side of that is, IF your kid is going to rid AT ALL at night, shouldn't they be using an effective light, both to see and be seen? Obviously the answer is yes. I could easily see someone rationalizing, "It's only a kid. Get them an inexpensive light." . . . which would translate into, "It's only a kid. Get them an ineffective light."
